Map scale describes the relationship between a distance on a map, in relation to the distance on the actual ground.
For example, for a map with a scale of 1:50,000, every measurement you make on the map is 50,000 times bigger in the real world.
So if you measure 1cm on the map, it equates to 500 metres on the ground (1cm x 50,000).
Similarly, a 1:25,000 scale map is 25,000 times bigger in ‘real life. So if you measure 1cm on this map, it will equate to 250 metres on the ground.
What is a map scale used for?
Map scale is used to allow you to accurately measure distance on a map, with it then being able to be directly transferred over to the real world and vice versa.
Simply put, map scale tells you how many times smaller your map is in relation to the real world, or, how many times bigger the real world is in relation to your map.
See definition of map scale below for more info.
How big is a grid square on a 1:50000 map?
A grid square on the 1:50,000 scale, is 2cm x 2cm in size, as opposed to the 4cm x 4cm for the 1:25,000 scale.
So, although the size on the map is different, the grid squares represent a 1km x 1km square on the actual ground for both scales. Hopefully, that’s not confusing.
As you can see, the 1:50k map’s 1km grids are smaller (2cm). This means that the map can cover larger areas, which at times has its advantages.
On the other hand, the 1:25k map’s grids are larger, with the total map covering an overall smaller area, but because the grids are larger, the map is ‘zoomed in’ and therefore shows more detail.
The Royal Marines training aid and helps explain this further:
Marines – how to read a map video
Definition for map scale
The definition for map scale is the relationship between distance on a map and the distance in the real world.
Map scale is the number of times that a map is smaller than the ground that it represents.
Or if looked at the other way round, map scale is the number of times that the real world is bigger than the area on a map that represents it.
As above, a 1:50,000 map means that the real world is 50,000 times bigger than the related area on the map.
How to calculate map scale
Should you have a map and not know what the scale is, perhaps because you are missing a section, or you just want to check one is what it says it is, you need to do the following:
For this method to work, you need a map that actually covers the location that you are in.
Choose a section on the map that you can measure in the real world. This should preferably be two easily identifiable landmarks, that are easy to identify on the map, as well as in the real world.
An example would be the distance between two bridges that are on the same road.
Now measure out the distance between the two bridges in the real-world. You may need to pace this out.
Then, measure the distance between the two bridges on the map.
Now calculate as below:
Map distance *divided by* distance on the ground = Map scale
Fo the above to work, you must use the same units of measurement. For example, you are probably going to measure the map distance in centimetres – and the real world in metres.
You will have to convert the real-world distance to the same units for the formula will work – so convert the metres into cm.
How do you find the scale of a map?
You can either use the formula mentioned above or in the majority of cases, you will find the map scale printed on the actual map itself.
If in the UK, we generally use 1:25000 and 1:50:000 scales, so it will likely be one of them.
However, many other scales are used across the world, so be sure to check yours.
Map scale calculator (table)
|Scale||1cm on map represents (on ground)||Example uses|
|1:10,000||100 metres||General in-car navigation|
|1: 25,000||250 metres||Used for Ordnance Survey maps|
|1: 50,000||500 metres||Used for Ordnance Survey maps|
|1: 100,000||1000 metres (1km)||Adventure touring, 4 wheel driving|
|1: 250,000||2.5km||Adventure touring, 4 wheel driving|
|1:1 million||10km||Tourist maps|
Map scale is simply the ratio of the map distance against the actual ground it represents.
It can take a bit of getting your head around this at first, but when you think about it, it’s actually very simple.
Looking for more on maps? We have written a full detailed post on the fundamentals of map and compass navigation where even the most seasoned navigator should pick up a thing or two!
Get it here.